Internal Conversion (IC) Rate Constant¶

Overview¶

MOMAP is able to calculate internal conversion (IC) rate constant, which is based on TVCORF_IC [1] and TVSPEC_IC subprograms. TVCORF_IC subprogram is used to calculate thermal vibration correlation function (TVCF). TVSPEC_IC subprogram is used to determine the relationship between IC rate constant and energy gap.

In the following part, this kind of calculation will be called nonrad calculation.

Calculate non-adiabatic coupling matrix element (NACME)¶

Unlike rad_FL calculation, NACME should be obtained before performing a nonrad calculation.

In MOMAP, get-nacme function is used to read transition electric field and vibration information from Gaussian output and calculate electronic coupling term. This process is integrated into evc subprogram. User needs to provide Gaussian electric field calculation result and toggle on NACME calculation in evc.inp. The rest steps are the same as evc calculation. After the calculation, a *.nacme file will be generated and it is used in nonrad calculation.

Start running calculation¶

To start a nonrad calculation, you need a evc.*.dat file, a *.nacme file, a job control file and a parallel control file. evc.*.dat file is the evc calculation result. *.nacme is the NACME calculation result. Job control file is used to generate an input for TVCORF_IC and TVSPEC_IC subprograms and implement parallel computation. Parallel control file is used to control computation nodes.

There is an example of performing nonrad calculation on 6T. The input files can be found in examples/6T/ic. 5 files are required in this example.

evc.cart.dat evc calculation result.
evc.cart.nac NACME result.
job Generate input file and implement parallel computation. Computation parameters are involved in this file.
run Set file path for job file and nodefile and run the calculation.
examples/config/nodefile Control computation nodes. The file path should be designated in run file. Other examples can be found in examples/DSB/ic and examples/azulene/ic.

Modifying job file¶

Here is an example of job file. Control parameters and their functions are listed down below. Change the parameters before performing a nonrad calculation.

&control
  DUSHIN      = .t.             # Toggle Duschinsky rotation effect
  Temp        = 298             # Temperature
  tmax        = 3000 fs         # Integral interval of correlation function (Must be converged. See section 4.4)
  dt          = 0.01 fs         # Integration step of correlation function (As small as possible)
  Ead         = 0.118042 au     # Adiabatic energy difference between two states (Able to change unit)
  logFile     = "log"           # Name of output info file (output)
  DSFile      = "evc.cart.dat"  # Name of evc file (input)
  CoulFile    = "nacme.out"     # Name of NACME info file (input)
  FtFile      = "ft.dat"        # Name of correlation function info file (output)
  isgauss      = .f.            # Toggle spectrum broadening
  BroadenType  = "lorentzian"   # Type of broadening function (lorentz / gauss)
  Broadenfunc  = "time"         # Type of broadening parameter (freq / time)
  lifetime     = 1.0 ps         # Broadening width (FWHM)
  NScale       = 10
  Emax         = 0.5 au         # Upper bound of spectrum
  FoFile       = "fo.dat"       # Name of spectrum info (output)
/

Verify convergence of correlation function and obtain results¶

Make sure the correlation function is converged. The verification process can be found in section 4.4.

Internal conversion (IC) rate constant can be found at the end of log file. The relationship between IC rate constant and energy gap can be obtained from fo.dat file.

[1]	`TVCORF_IC_para` subprogram is available for parallel computation.